The semiconductor industry is under continual pressure to shrink features sizes so that processing power may be packaged into increasingly smaller dimensions. Because of the minute dimensions required in the fabrication of semiconductor devices, exacting control of processes used to manufacture semiconductor devices may be desirable in order to achieve acceptable and reproducible results. Measures for maintaining process integrity may include: utilizing ultra-clean environments, creating ultra-pure chemical process agents, and strictly controlling ambient conditions. In utilizing these measures, process steps may be more strictly controlled. One particular process step conventionally utilized for semiconductor fabrication is one or more pre-cleaning or cleaning operations performed on a substrate.
For example, a pre-cleaning operation may be utilized to prepare a substrate for a capping process. As may be appreciated, capping processes form a capping layer that significantly reduce electromigration associated with copper lines. In addition, capping layers may reduce an effective dielectric constant of copper/low-k dielectric interconnect structure. In a capping process, a pre-cleaning step may be utilized to remove organic and inorganic contamination on wafer surfaces while minimizing corrosion of the copper lines. Conventional pre-cleaning processes typically utilize commercially available cleaning solutions that may include organic acids, alkyl-alcohol amines, and anti-oxidants. These solutions may be pH adjusted in accordance with desired chemical reactivity for a particular substrate or process.
In a cleaning (e.g. a pre- or post-clean) process step, solutions may be applied to a substrate in any number of manners such as, for example, a solution bath. Controlling the chemical composition of a cleaning solution bath within an optimized concentration range or process window is critical to ensure reproducible results and optimal process performance. However, in some conventional systems utilizing commercially available chemistries, semiconductor manufacturers often rely solely on the purity and the concentration of the originally acquired cleaning solutions, which may not always provide for optimal results. Thus, systems and method for monitoring and controlling combinatorial processes are presented herein.